<template>
  <div class="spec-preview" @mousemove="mousemove">
    <img :src="skuImageList[defaultIndex]?.imgUrl"/>
    <!--    大的遮罩层-->
    <div class="event" ref="event"></div>
    <!--    大图-->
    <div class="big">
      <img :src="skuImageList[defaultIndex]?.imgUrl" ref="defaultImg"/>
    </div>
    <!--    可拖动遮罩层-->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  data() {
    return {
      defaultIndex: 0
    }
  },
  mounted() {
    this.$bus.$on('changeIndex', (index) => {
      this.defaultIndex = index
    })
  },
  props: ['skuImageList'],
  methods: {
    mousemove(e) {
      const mask = this.$refs.mask
      const event = this.$refs.event
      //获取鼠标距离盒子左边的距离
      const mouseOffset = {
        x: e.offsetX,
        y: e.offsetY
      }
      //获取mask距离的一半
      const maskHalf = {
        x: this.$refs.mask.offsetWidth / 2,
        y: this.$refs.mask.offsetHeight / 2
      }
      //计算mask的实时位置
      const resPosition = {
        x: mouseOffset.x - maskHalf.x,
        y: mouseOffset.y - maskHalf.y
      }
      if (resPosition.x < 0) {
        resPosition.x = 0
      } else if (resPosition.x >= event.clientWidth - mask.offsetWidth) {
        resPosition.x = event.clientWidth - mask.offsetWidth
      }

      if (resPosition.y < 0) {
        resPosition.y = 0
      } else if (resPosition.y >= event.clientHeight - mask.offsetHeight) {
        resPosition.y = event.clientHeight - mask.offsetHeight
      }
      this.$refs.mask.style.left = resPosition.x + 'px'
      this.$refs.mask.style.top = resPosition.y + 'px'
      //设置大图的位置
      this.$refs.defaultImg.style.left = -resPosition.x * 2 + 'px'
      this.$refs.defaultImg.style.top = -resPosition.y * 2 + 'px'
    }
  }
}
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>